Why the crime drop? Why crime rates fall and why they don’t

The ‘crime drop’ is the most important criminological phenomenon of modern times. In North America, Europe, and Australasia, many common crimes have fallen by half or more since the early 1990s, albeit with variation in the specifics. Seventeen explanations are examined here including demographics, policing, imprisonment, drug markets and lead poisoning. Some have been falsified, some lack evidence, some are inconsistent with the evidence, and some claim a minor contribution at most. Pioneering research that developed explanations only relevant to the United States now appears, with the benefit of hindsight, somewhat parochial. Sixteen of the seventeen hypotheses fail one or more of four evidence-based standardized tests on which they are assessed. The one that passes is the security hypothesis, underpinned by crime opportunity theories. Here there is strong evidence from four countries that vehicle theft fell due to more and better security, and mounting evidence that improved security was critical in reducing burglary and other acquisitive crime. Many crime types are inter-related, while most criminal careers are dominated by property crime, so removing these volume crimes might be expected to reduce violence. The policy implication of the security hypothesis is that governments should promote regulation and incentives to promote designing-out crime and crime-proofing for the remaining common crimes plus new and emerging crime types